Timing device



Feb. 27, 1945. s. J. BEGUN 2,370,134

TIMING DEVICE Filed Aug. 21, 1942 4 Sheets-Sheet 2 llllllllhkl62 W HG. 5

Feb. 27, 1945. s. J. BEGUN 2,370,134

' TIMING DEVICE Filed Aug. 21, 1942 4 Sheets-Sheet 3 mwN/Uff- Feb. 27,1945. s. J. BEGUN 2,370,134

' TIMING DEVICE Filed Aug. 21, 1942 4 Sheets-sheet 4 wr FI E. 9 f

FIB. IU

Patented Feb. 27, 1945 E TIMING DEVICE Semi Joseph Begun, ClevelandHeights, Ohio, as-

signor to The Brush Development Company,

Cleveland, Ohio, a corporation of Ohio Application August 21, 1942,Serial No. 455,646

27 Claims.

My invention pertains to timing devices, and more particularly todevices adapted to time short intervals with a high degree of accuracy.

An object of my invention is to provide an ccurate short interval timingdevice.

Another object of my invention is to provide a small portable timingdevice.

A further object of my invention is to provide an accurate timing devicewherein the degree of accuracy is constant even though the device ismoved from place to place.

It is another object of my invention to provide a timing device theaccuracy of which is substantially independent of mechanical means.

It is also an object of my invention to provide a timing device forquickly giving an accurate indication of a short time interval.

Another object of my invention is to provide a method oi' and the meansfor measuring the duration of long time intervals with the same highdegree of accuracy with which I measure short time intervals.

Other objects and a fuller understanding of my invention may be had byreferring to the following speciiication and the accompanying drawingsin which:

Figure l is a block diagram illustration of a form of my invention.

Figures 2 to 4 show diagrammatically the action of my invention on asinusoidal wave.

Figure 5 illustrates a circuit which may be used in place of the circuitshown in Figure 1.

Figure 6 illustrates a timing device adapted to time long intervals;

Figure 7 illustrates a timing device for measuring such distances as thedepth of the ocean.

Figure 8 illustrates another device for measuring depths and distances.

Figure 9 illustrates a circuit for use with some of my other deviceswhereby certain parts of the devices may be eliminated; and

Figure 10 is an illustration of an electronic circuit for timing shortintervals.

This application is related to Frederick J. Hoovens application SerialNumber 469,237, for a Timing device, wherein an alternating signal isrecorded on a moving record member during an interval to be timed, andthereafter the record is repeatedly reproduced to establish analternating electrical signal which is applied to a calibrated meter forgiving an indication of the duration of the time interval. In the Hoovendevice the rate of oscillation of the alternating signal which isrecorded need not be known or accurately controlled as to frequency.

This application is also related to Otto Korneis application SerialNumber 447,985, Means for and a method oi measuring; and to my previousapplication Serial Number 437,395, Means for and a method of timing.

This application is primarily directed to means for obtaining themeasurement of a time interval having a duration longer than timenecessary for one cycle of the signal storage member; and to the featureof utilizing a biased electronic element whereby electrical signalscorresponding to noise on the unrecorded portion of the record track onthe signal storage member are prevented from actuating a time intervalindicating device; and to the combination of the aforementioned biasedelectronic element with an amplier which strongly amplifles thereproduced signal which is to be supplied to the indicating device andchopping oil" the peaks of the strongly amplied signal to improve theaccuracy of the system.

Figure 1 illustrates in block diagram form a system for indicating atime interval in which reference character I0 represents a moving recordmember such for example as an endless magnetizable tape or disk ofmagnetizable material which is moving at a known and constant rate o1'speed. Positioned near the moving magnetizable material is a magnetichead indicated generally by the reference character I3 and comprised ofa pole piece II which is in magnetic ux linkage relationship with thedisk I0, and a coil I2 wound around the pole piece II.

An oscillator I4 is provided and its signal output y is amplified by theamplier I5 and is connected t to the coil I2 of the magnetic head I3.Between the oscillator Il and the amplifier I5 there is a switch I6which is operated by a trigger circuit in accordance with the intervalto be timed. The trigger circuit is preferably electronic and may befired by any relay action, by photoelectric cells, vor by bridgecircuits, etc. It is also obvious that a mechanical trigger circuitcould be used if it was desired, but mechanical actuation of the switchIB may be less rapid and accurate than electronic actuation. An intervalis timed by the trigger circuit closing switch I6 at the beginning ofthe interval, thereby establishing on the moving disk Ill a magneticrecord of a number of oscillations of the oscillator I 4. During thisprocess the magnetic head I3 is a recording head and the signal currentfrom the amplifier I5 passing through the coil I2 establishes .a varyingmagnetic iiux in the pole piece I I and in the disk I0 which is passingclose to the pole piece. The length of the record made on the disk I0 isdirect- I6 was closed, and as this length of time was govv erned by theinterval controlled trigger circuit the length of the record on the diskI must be directly proportional to the length of the interval to betimed.

Several methods of determining the length of the time interval from therecord member I0 may be used. One of them comprises the steps ofrepeatedlyv reproducing the record from the disk I0 to establish asignal which is amplified by the amplier 2l, and then applying theamplied output signal to an oscilloscope 20 and there counting thenumber of cycles of the oscillator which were recorded. This process wasshown, described, and claimed in my application Serial No. 437,395. Thebasis for accuracy in this system is the accuracy and stability of theoscillator. The number of oscillations per second must be known. i v

Another method of determining the length of the time intervalirom therecord member is to know the rate of rotation of the record memberduring the recording -process and to determine by some means the ratiobetween the length of recorded signal and the total length of therecording track on the disk IIJ.

In order to determine the length of the recorded portion of the signaltrack on the disk I0, the coil I2 is disconnected from the recordingcircuit and is connected to the reproducing circuit thereby establishingthe head as a reproducing head. The disk is driven past the pole pieceII at a constant rate of speed, and the magnetic pattern in the diskwill establish in the pole piece II a varying magnetic flux whichinduces in the coil I2 an electromotive force. The electromotive forcegenerated in the coil I2 is amplied by the amplier 2 I, and theamplified output is passed through one or more limiters 22 which chopoff the peaks of each half wave length in order to reduce error due tovariable amplitudes of the reproduced wave. The llmited wave is then fedinto a full Wave rectifier 23 and from there to a current averagingmeter 24 such, for example, as a milliammeter. Each revolution of thedisk I0 causes an amount of current to be applied to the meter for aperiod of time which bears a direct relationship to the length of themagnetic pattern on the disk and it therefore has a direct relationshipto the length of the interval to be timed. Because the meter 24 is ofthe averaging type the hand will give a Steady indication after a fewrevolutions of the magnetizable material. The scale on the face of themeter may be divided into units of time.

Two sources of error or inaccuracy may exist in this system. The firstmay be due to the variable amplitudes of successive cycles of thereproduced wave brought about by causes such as variations in themagnetizable disk I0. To reduce the error which may be due to this, Igreatly amplify the signal picked up from the disk I0 and pass theamplified signal through the limiter 22 before it reaches the meter 24,thus obtaining signals of the same amplitude and approximately the sameshape. Another source of error which may exist in this system is aVmeter reading arising from background noise which is always present inrecording and reproducing systems. Background noise on the unrecordedportion of the disk will cause the meter to indicate a value which iserroneous, and background noise superposed on the signal correspondingto the interval to be timed will also introduce error. The error due tobackground noise superposed on the signal will be greatly reduced due tothe action of the ampliller 2| and the limiter 22, but the other errorremains undiminished. In order to reduce this other error I provide adetector 23 between the head I3 and the meter 24, which is so biasedubybattery 25 that any signals which are stronger than the background noisewill be rectified, and the voltages caused by the background noiseitself will be Ibelow the cut-off voltage of the rectier.

The averaging meter 24 has previously been calibrated by recording thecurrent output of the oscillator I4 on the disk I0 for a known portionof one revolution of the disk and then reproducing the signal throughthe limiter 22 and the detector 23 to the meter 24. The signal recordedon the portion of the disk I0 will cause the hand of the meter to read acertain value; if, for example, the known portion which was recorded onthe disk I 0 was the entire length of the recording path on the disk,the meter can be adjusted to read units. The duration of the interval tobe timed must be no-t longer than the duration for one completerevolution of the disk I0. Accordingly, the record on the disk I0established by the interval to be timed will extend over less than theentire length of the recording path on the disk, and when the record isreproduced and the output signal applied to the meter 24, the hand willindicate some value less than 100 units; say for example 50 units. Theportion of the disk on which a recording was made is therefore 1/2, a'ndknowing the rate of rotation of the disk I0; say for example 60revolutions per second, the duration of the time interval may bedetermined to be 1/120 of a second. It is obvious that the scale for themeter may directly indicate the time interval. That is, instead ofreadinglOO units or 50 units the hand would indicate Mm of a second and1/120 of a second. The accuracy of this system depends primarily uponthe rotation of the magnetizable record material at a known and constantrate, and the constancy of the Oscillator is of secondary importancealthough it is advisable to use one which is fairly constant.

Another manner of reproducing the signal from the disk I0, and in whichthe rate of rotation of the disk is immaterial so long as it isconstant, is to calibrate the meter 24 by reproducing the signal intothe oscilloscope and counting the number of cycles which were recorded.If the meter deflects 100 divisions for 100 cycles of the oscillator,and the rate of oscillations is known as, for example 100,000 cycles persecond, the time interval the meter reads will be one millisecond, andeach meter division would represent l0 microseconds. After the meter hasbeen cali brated the subsequent readings may be made without rstapplying the signal to the oscilloscope 20 and a great saving of timewill be effected. 'I'his system uses cycle counting for Calibrating themeter 24, and thereafter uses an integrating process for obtaining theindication.

Another method which may be used for calibrating the meter 24 is toapply a signal corresponding to a known time interval to the recordingcircuit, and repeatedly reproducing the disk record caused by the knowntime interval to establish a reproduced signal. The reproduced signalcan then be limited, rectified, integrated and the value read on thescale of the meter. The deflection of the meter hand caused by the knowntime interval calibrates the meter. and subsequent deiiections torunknown time intervals con then be directly read on the meter.

Figures 2 to 4 illustrate ldiagrammatically the action of my inventionon a wave which is reproduced from the magnetic impression made in themagnetizable recording material and which has amplitude variations.These variations result from the diiferences in the magneticcharacteristic of the magnetizable material for different points alongthe path of recording. This variation in amplitude is illustrated inexaggerated form in Figure 2 by showing the rst cycle ofgreateramplitude than the subsequent cycles, and the background noise isillustrated by the waviness in the line. The signal shown in Figures 2,3, and 4 is not sinusoidal because I am recording on a saturatedmagnetizable material without using a polarizing current, therebycausing one-half of the signal to be in the saturation range. .Asinusoidal wave could have been recorded by using a neutralized tape, orby using a saturated magnetizable material and a polarizing current.

In Figure 3 the action of the limiter is shown. The limiter chops oi andattens the peaks of every other half cycle.

The portion of the signal above the line 42 is effectively eliminated,and accordingly the inaccuracy due to the amplitude variation is greatlyreduced.

The rectifier action is illustrated in Figure 4. The half-cycles of thesignal which are not subjected to the limiter action are chopped off andthrown away, and due to the bias on the rectifier the amount of thesignal discarded can be adjusted to include all or substantially all ofthe background noise on the unrecorded portion of the signal track. InFigure 4 this bias 'value is illustrated by the line 4l. The shadedportions 43, 44 comprise the signal which is passed to the averagingmeter 24.

Figure 5 illustrates diagrammatically another circuit which may be usedin my device in place of the reproducing circuit shown in Figure 1. Thesignal from the reproducing head I3 passes to a preamplifier 60 and thento a detector BI which is so biased by a battery 62 as not to be aiectedby the background noise signal at the portions of the disk where norecording is made, thereby reducing error due to the background noise onthe magnetizable material. The signal which leaves the detector 6Icorresponds to the recorded signal only, but on this signal issuperposed a small amount of noise signal. From the biased detector 6|the signal passes to the amplier 63 and then to the limiter whichreduces error dueI to the amplitude variation, and then to the averagingmeter 24. On this limited Wave the residual eiect of the backgroundnoise superposed on the recorded signal is greatly reduced.

It is desirable for best results that the frequency of the oscillatorshould be such as to give the best signal to noise ratio. For somematerials and speeds of the signal carrier this frequency may be in therange of 10,000 cycles per second. In some devices it is conceivablethat this best frequency cannot be used. In such a case equalization maybe used it it is needed.

The timer arrangements described have the disadvantage that they do notpermit the measuring of a time interval longer than the time for themagnetizable material to make one complete revolution. For many usesthis may be a disadvantage. Accordingly, I provide a means for and amethod of accurately timing intervals which are long compared to thetime of one revolution of the record material. In Figure 6 there isshown a disk In of magnetizable material which is rotated at a known andconstant rate of speed by a motor 46. Associated with the disk AIll aretwo magnetic recording heads 41, 48, and two reproducing heads 49, 50.The recording head 41 and the reproducing head 49 are located on track Aon the disk I0, and the reproducing head 49 is adapted to pick-up thesignal which the recording head 41 impresses on the disk, and therecording head 48 and reproducing head 50 are on track B and are adaptedto cooperate in the same manner. An obliterating head 5| is positionedbetween the reproducing head 50 and the recording head 48, and extendsonly across track B, thus preparing the track for a new record. Thereproducing head 49 also serves part time as an obliterating head.

When an interval is to be timed the motor 46 is started and the disk I0is driven at a known and constant rate of speed. Switches 52 and 53 arenormally open. At the start of the interval to be timed switch 52 isclosed thereby connecting the output signal from the oscillator 54through the amplifier 55 to both recording heads 41, 48. Switch 53 isalso closed thereby connecting the battery 56 to the head 49 therebymaking head 49 an obliterating head. During the time that it' takes thedisk I0 to rotate lthrough the angle a both of the recording heads 41,48 are recording the signal from the oscillator 54. signal recorded byhead 48 on track B reaches the reproducing head 50, an electromotiveforce is generated which is ampliiied by the ampliiier 58, and theoutput is used to actuate the counter 51 and to reduce the gain in theamplifier 55 to prevent the heads 4l, 48 from further recording for aninterval of time t equal to the length of time it takes the disk torotate through the angle a. When the magnetic pattern which was recordedon track A reaches the head 49 it is obliterated by magnetic flux set upby a current from battery 56.

The signals recorded on tracks A and B of the magnetizable disk l0 arealternating signals as they were derived from the oscillator 54. Thereproducing head 50 establishes an alternating electromotive force whichblocks the amplifier 55 thereby preventing the further recording of asignal on the disk I0 for an interval of time t equal to the length oftime it takes the disk to rotate through angle a.

Accordingly, reproducing head 50, after the start of an interval to betimed, does not pick up any signal for the time t. Then for a period oftime t it picks up a signal. For the next period t no signal is pickedup etc. It Will be seen that the head 50 picks up a signal in the timeintervals t to 2t, 3t to 4t, 5t to 6t, etc., but does not pick up asignal in the time intervals 0 to t, 2t to 3t, 4t to 5t, etc.

From the amplier 58 the signal passes to a rectifying and integratingdevice 10 to establish substantially a D. C. pulse having a durationcorresponding to the duration of the alternating signal. This D. C.pulse blocks amplifier 55 and is also fed to a differentiating device1I. The output signal from the dierentiating device consists of a seriesof pulses occurring at time intervals t, 2t, 3t, 4t, 5t, etc., and eachpulse causes the counter 51 to move one step for each period of timeduring which the disk rotates When the magnetic pattern of the,6(-)etc.-. Unless the interval to be timed is exactly as long as thelength of time for a whole even number of revolutions of the disk I8through the angle a there will be a signal recorded on track A which hasnot been obliterated by the head 49. The duration of this signal must beadded to or subtracted from the interval indicated on the counter 51.The duration of this signal will be indicated on the scale of theindicating device 24, and will be subtracted from the counter indicationif the counter says and added to the counter indication if the countersays The head 49 serves as an obliterating head only during the intervalto be timed.. During the ilrst time interval t the obliterating head 49will be energized by the battery 55 but will not obliterate a signalfrom track A as there is no signal recorded on that portion of track Awhich is passing head 49. During the second time interval t the head 49will obliterate the signal from track A.` During the third time intervalt there will be no signal obliterated etc.

At the end of the interval to be timed the switches 52 and 53 aresimultaneously thrown by the trigger circuit to break the contactbetween the oscillator 54 and the recording heads 41, 48 therebyterminating all recording, and to break the contact between the battery56 and the obliterating head 49 thereby terminating the obliteratingfunction of head 49, and to make a contact from the head 49 to theamplier 2| thereby establishing the head 49 as a reproducing head.Simultaneously with the throwing of switches 52, 53 the switch 59 isthrown to break the circuit from reproducing head 50 to the counter 51in order that there will be no further actuation of the counter whichcould arise from the end of the signal recorded on track B passingthrough v the head 58. Without switch 59 the signal, if it occurredsometime during 2, 4, 6, or St, would establish a pulse which wouldactuate the counter 51, thereby introducing an error.

For reasons of simplicity I have shown switches 52, 53, and 59 asmechanical and actuated by the trigger circuit switch I6, but it is tobe understood that electronic switches may be used, as a more rapidaction could be obtained thereby reducing the amount of error due totime lag in switching.

The signal which was recorded on track A and was not obliterated by head49 before switch 53 was opened will, upon repeatedly rotating it pastthe pickup head 49, establish an electromotive force. The electromotiveforce is amplified by the amplifier 2l, and passes through the limiter22 and the detector 23, and is applied to the calibrated currentaveraging device 24 as has been previously described.

The time interval is measured by algebraically combining the readings onthe counter 51 and meter 24. The counter indicates whole time in..tervals t, and the meter 24 indicates a portion of a time interval t.The meter indication is to be added to the counter indication if thecounter says and is to be subtracted from the counter indication if thecounter says In order that my device may be clearly understood thesuccessive operations will be described through the angle. a.Thefcounter starts with (lll agrandir.-

in connection .with timing a given interval. For example: Suppose it isdesired t0 time an interval of 275 microseconds, and the time of onerevolution of the disk I9 is 100 microseconds. It is apparent that thetime for the vdisk to rotate through the angle a is 75 microseconds.Before the start of the interval to be timed switches 59. 52, and 53 areopen, the disk I8 is rotating, and the oscillator 54 is operating.

At the start of the interval to be timed switches 59, 52, and 53 aresimultaneously closed thereby connecting the counter 51 (which registers0+) to the reproducing head 59 and connecting the battery 55 to the head49 to establish it as an obliterating head, and connecting theoscillator 54 to the recording heads 41, 48 to initiate recording onboth tracks A and B. After 75 microseconds the front of the record ontrack B starts to pass reproducing head thereby simultaneouslyinitiating two actions. One action causes the counter 51 to change itsreading from 0+ to 2-, and the other is to block the amplifier 55 tostop the recording on tracks A and B. As long as a signal passes head 50there will be no recording by heads 41, 48. At the same time that thestart of the signal on track A reaches reproducing head 50 the start ofthe signal on track B reaches the obliterating head 49. The record ontrack 49 will be obliterated for 75 microseconds until the end of thesignal on track B passes head 50, at which time amplifier is unblockedand recording is again started at heads 41, 48, and the counter 41 isactuated to read 2+. By this time 150 microseconds have elapsed. For thenext microseconds heads 41, 48 record on tracks A and B and when thefront ends of the records reach heads 50 and 49 the counter is moved to4- and the recording by heads 41, 48 is again blocked. 225 microsecondshave now elapsed. For the next 50 microseconds until the switch 53 isopened by the end of the interval tobe timed the obliterating head 49obliterates the record on track A, thereby leaving a record only 25microseconds long on track A. The end of the interval to be timed alsoopens switches 59 and 52. Switch 53 connects the head 49 to the meter 24and it now functions as a reproducing head. Upon repeatedly reproducingthe record remaining on track A the meter 24 will indicate 25 m1-croseconds, and because the counter read 4- the 25 microseconds will besubtracted from 300 microseconds (4 '75=300) to give an interval time of275 microseconds.

A condenser discharge type of obliterating device may be provided forrendering the magnetic condition of track A uniform before a newinterval is timed. Normally the switch 15 is open. After an interval hasbeen timed and the operator desires to clear track A, he presses pushbutton 16 thereby closing switch 15 and connecting the battery 18 to thecoil of the obliterating head 19. The current from the battery 18 issufficient to saturate the portion of the disk l0 which is under theobliterating head 19 and is applied for at least one revolution, andwhen the push button is released the condenser 11, which has beencharged by battery 18, discharges through the coil of the obliteratinghead thereby gradually reducing the flux which is applied to themagnetizable disk l0. 'This type of obliteration due to the condenserdischarge does not leave a sharp change in the amount of magnetizationin the portion of the disk which was under the head 19 when the switch15 was opened,

thereby preventing the actuation of the counter I1 by the sharp changein magnetization.

A use to which my device may be put is to measure the time which elapsesbetween transmitting a signal toward a reflecting surface and receivingthe reflected echo oi' the signal. Im'- portant applications of thissystem are measuring altitude, measuring the depth of water, anddetermining the distance a submarine 'body is from the operator. Aconvenient system is described in Figure 'I in which a magnetizable diskis rotated by the motor |0| at a uniform rate of speed. The motor |0| isprovided with reduction gears |02 and a cam disk |03 which has a raisedportion |04. The gear reduction system is such that the cam disk |03makes one revolution for several hundred revolutions of the magnetizabledisk |00. The raised portion |04 controls the opening and closing ofthree switches |05, |08, and |01 which are normally biased to their openposition. The obliterating switch |05 makes and breaks a circuit in theobliterating oscillator |08 which feeds the magnetic obliterating head|08. When the raised portion |04 on the cam disk |03 closes the switch|05 current ows from the oscillator |08 through the windings of theobliterating head 09 thereby establishing a magnetic flux through thedisk |00 which saturates the portion of the disk which is between thetwo pole pieces of the obliterating head, and as that saturated portionof the disk moves away from the obliterating head the intensity of themagnetic field gradually is reduced. Due to the alternatingcharacteristic of the current through the obliterating head and thegradual decrease in the intensity of the magnetic field as eachincremental portion of the disk |00 moves away from the pole pieces,each portion of the disk which has passed between the pole pieces isdemagnetized to substantially its virgin magnetic state. The switch |05must be held closed for a length of time which is greater than thelength of time for one revolution of the magnetizable disk |00, and thenreleased to prevent further obliteration. Arrangements may be made inthe oscillator |08 so that when switch |05 is opened an abrupt breakingof the current to the head |00 is avoided.

After the magnetizable disk |00 has been obliterated the raised portion|04 simultaneously closes the switches |06, |01 and |28 each of which isheld closed for only a very short interval of time. The switch |01 makesa circuit through the impulse generator ||0 which causes a short signalto be sent out from the transmitter toward the distant object whichreflects the signal back to the receiver ||2. Switch |28 short circuitsthe amplifier ||6 during the transmission of the pulse so that thedirect signal will not affect the trigger circuit |4. Simultaneouslywith the closing of switch |01 the switch |06 is also closed therebyconnecting the battery ||3 to the trigger circuit which is indicatedgenerally by the reference character ||4, initiates the triggering andcauses a current to iiow in the recording coil ||5. When the reflectedsignal arrives at the receiver ||2 it is amplified at the amplier I6 andan impulse is applied to the trigger circuit H4 to stop the current inthe recording coil ||5. Between the time the impulse was sent out of thetransmitter I. and the time the reflected signal was received at thereceiver ||2 a signal was being recorded on the rotating disk |00.Knowing the rate of rotation of the disk |00 the length of time can bedetermined by repeatedly reproducing the signal to establish a currentin the reproducing coil ||1 which is applied to a measuring device |21which, for the device shown in Figure 7, may be a circuit similar tothat shown in Figure 10, or if an alternating current had been recordedon the disk |00, a reproducing circuit similar to those shown in Figure1 or 5 could have been used.

One suitable trigger circuit ||4 is described in Electronics, November,1940, page 29,` in which two thyratron tubes H9 and |20 are used. Tobegin with no current flows through the tubes because of the negativevoltage applied to their grids through resistance |2| from battery |22.When the switch |06 is closed by the raised portion |04 on disk |03 thepositive bias applied by Jbattery ||3 through the condenser biases thethyratron tube ||9 allowing a current to flow vfrom the batter |23through resistance |24. This current flows through the recording coil I5and establishes a magnetic pattern on the rotating disk |00. When thereected signal is received at ||2 and ampliiied a positive impulse isapplied to the grid of tube |20 thereby firing it and connectingbatteries |23 and |25 in series through resistance |24 and tube |20.This results in an increase of voltage drop across the terminals ofresistor |24, and lowers the potential of the plate oi' tube 9 to thepoint where it extinguishes, thus cutting oi the current through therecording coil ||5 and stopping the recording. A switch |26 is providedin the plate circuit of the tube |20, and is opened by raised portion|04 of the disk |03 after the timing operation has been completed,thereby breaking the bias on the tube and restoring the device to normalfrom whence a. subsequent timingoperation can be performed. Obviously,many other diierent kinds of trigger circuits could be used.

Another device for measuring depths and distances by the reflected echomethod is illustrated in Figure 8 in which the motor |0| drives themagnetizable disk |00, and in addition drives two other disks |30 and|3|. The disk |30 has a raised portion |32 which closes a switch |34which is normally biased open, and the disk |3| has a raised portion |33which closes two switches 35 and |36 both of which are normally biasedopen. The disk |3| periodically closes the switches |35 and |36 for veryshort time ini/ervals. For example, the switch |35 may be held closedfor miscroseconds and the switch |36 may be held closed for 40microseconds. The switch |34 is held closed for a somewhat longer timeinterval. The order of closing is first switch |35 and thensimultaneously switches |36 and |34. The order of opening is firstswitch |36, then switch |35, andfinally switch |34. The switch |35 shortcircuits the input line of the receiver ||2 to render the receiverinoperative during the time a signal is being sent out from thetransmitter Switch |36 connects the sound source ||0 with theVtransmitter and at the same instant when switch |31 is manually heldclosed, switch |34 initiates the timing period by starting a recordingon the disk |00 by connecting the battery |38 to a Winding |40 on therecording head. The echo of the signal transmitted from is received at2, is ampliiied by the thyratron amplifier H6, and serves to stop themagnetic recording on the disk |00. The amount of recording on the disk|00 is an indication of the duration of the interval to be timed, and itmay be found by repeatedly reproducing the signal from the disk into anaveraging beginning of the magnetic signal corresponding.

to the beginning of the interval to be timed, and

a rapid decrease at the end of the magnetic signal corresponding to theend of the interval to be timed. Between the beginning and the end ofthe magnetic signal there will be very little change of magnetization inthe disk |00. In the reproducing process the reproducing head is onlyable to establish an electromotive force which is proportional to therate of change of iiux cutting the coil in the head; in other words thereproducing head picks up 1o/dt. Each revolution of the disk |00 uponwhich a unidirectional magnetic signal has been recorded will establishtwo short electromotive pulses, one corresponding to the beginning ofthe magnetic signal where the rate of increase of magnetization is high,and the other corresponding to the end of the magnetic signal where therate of decrease of magnetization is high. These two electromotivepulses will be of opposite polarity as one was established by anincrease in magnetization and the other was established by a decrease inmagnetization. Y

By using a glow lamp |45 which will flash under the control of anelectromotive force of either polarity I can make the device shown inFigure 8 operative to indicate both the beginning and the end of theinterval to be timed by repeatedly rotating the disk |00 therebyrepeatedly causing the glow lamp |45 to flash when a certain point onthe scale |46 is near the lamp. As the scale is synchronized with therotation of the magnetizable disk the stroboscopic eiect will cause onescale reading to appear to be superposed on another scale reading. Thedifference between the readings of the two scales is a measure of theamount the magnetizable disk rotated between the start and end of theinterval to be timed, and knowing the rate of rotation of themagnetizable disk during recording this .angle becom-es an indication ofthe duration of the interval to be timed. If capital T represents thelength of time of one revolution of the disk |00 during the recordingprocess, and small t represents the length of time during the intervalto be measured and which is less than T, then repeatedly reproducing thesignal on the magnetizable disk into an averaging meter gives the ratiot/T, and repeatedly reproducing the signal on the magnetizable disk tocause the glow lamp |45 to flash permits measuring an angle a which isthe angle through which the magnetizable disk |00 moves in time t. Inother words I have 'orovided means for measuring either t/ T or fit/360,either of which will give the length of the interval to be timed if therate of rotation of the magnetizable disk 00 during recordingr is known.In the eouation t/T the value of T must be known. In the equation 1r/360the length of time necessary for the disk to rotate through 360 degreesmust be known. This length of time is also T.

To determine, for instance, the depth of the ocean at a certain pointthe switch |31 is manually closed. Switch |35 short circuits thereceiver circuit and upon the raised portion |32 on disk |30 closingswitch |34 a circuit is made from battery |38, thereby causing a directcurrent to flow through the coil oi' the relay |33 and through therecording coil |40 of the magnetic head. The current in the recordingcoil |40 causes magnetic flux to pass through the disk |00 and leave aunidirectional pattern on the disk. The current through the coil of therelay |33 causes the contact |14| to close and establishes a parallelcircuit to switch |34 and switch |31 and at the same time establishes aholding circuit. At the same time switch |34 is closed to startrecording on the disk 00 the switch |36 closes for a short time intervaland causes a .signal to be sent from the transmitter The receiver ||2 isshort circuited and accordingly cannot receive a direct signal from thetransmitter, but before the echo arrives at the receiver ||2 switch |35is opened. The echo is'received at ||2 and amplied at ||6. The impulsestarts the operation of a thyratron from which current is passed throughthe coil |42 wound about the same pole piece as theA recording coil |40,but which is arranged to establish a magnetic flux which issubstantially equal to and bucking the flux established by the coil |40.Therefore, as soon as coil |42 becomes energized, the recording on thedisk |00 stops. A third winding |43 may be provided for reproducing therecord to establish two pulses, one at the beginning of the magneticrecord on the disk and the other at the end of the record on the disk.These pulses are amplified by the amplier |44 and ignite the glow lamp|45. The magnetizable disk |00 is provided with a scale |46 on its face,and the flash of the glow lamp illuminates the disk at two points duringeach revolution, one at the beginning of the interval to be timed andthe other at the end of the interval to be timed. The difference betweenthe two readings is an indi cation of the duration of the time interval.The device is reset by opening the switch which breaks the recordingcircuit to coil |40, and simultaneously breaks the circuit from thethyratron through the coil |42, and releasing the relay |4| By causingthe glow lamp to fire momentarily twice during each revolution of themagnetizable disk 00 two scale readings can be obtained by thestroboscopic effect. One of these readings subtracted from the otherreadings will give an indication of the amount of rotation of the disk|00 during the interval to be timed, thereby giving an indication of theduration of the interval to be timed. Unless precautions are taken errormay result from uncertainty as to which flash represented the beginningand which flash represented the end of the interval to be timed. Severalmethods of distinguishing one flash from the other are shown, described,and claimed in Otto Korneis co-pending application, Serial No. 447,985.In the device shown in Figure 8 I avoid this possibility of error bycausing switches |34 and |35 to be closed at the instant the zero pointof the scale |46 on the disk |00 is immediately under the glow lamp |45.The `operator will know that the flash of the glow lamp |45 which alwaysoccurs when the zero indication of the scale 46 is in line with the mark|41 corresponds to the start of the interval to be timed. Accordingly,the operator will also know that the other ash corresponds to the end ofthe interval to be timed.`

For convenience in making a device of this kind, it is suggested thatthe functions of the recording ampliiier Ill and the reproducing amplier|44 be combined into one amplifier. and that the transmitter and thereceiver Il! be combined into one unit.

In many applications of the above described nature and in which the glowlamp is not nred at a predetermined point on the scale correspondins tothe start of the signal, two glow lamps are convenient, one responsiveonly to the pulse generated in accordance with the start of-the magneticrecord on the disk |00, and the other responsive only to thepulse-generated in accordance with the end of the magnetic record on thedisk and a distinguishing feature such as color may be embodied with thelamps. A rectifier which passes only electromotive pulses correspondingto the electromotive pulse established by the reproducing head for thestart of the interval to be timed may be connected to a. red glow lamp,and a rectifier which passes only electromotive pulses corresponding tothe electromotive pulse established by the reproducing' head for the endof the interval to be timed may be connected to a green glow lamp. Inthis manner it is easy to distinguish between the pulse corresponding tothe start of the time interval and the pulse corresponding to the end ofthe time interval.

The circuit illustrated in Figure 9 provides a method for eliminatingone of the glow lamps `and still obtain an accurate and well definedreading. A switch |50 is provided in the playback circuit and. the disk|00 is repeatedly rotatedpast the reproducing head |52 to generate anoutput signal which is amplified by the amplifier |53. With the switch|50 thrown to connect the input of the rectiiier to the output of theamplifier |53, the signal is rectified and the pulse corresponding tothe end of the magnetic pattern on the disk: |00 is eliminated.Accordingly, the glow lamp 45 flashes only for the pulse correspondingto the beginning of the magnetic pattern. With the glow lamp 45 flashingonly for the pulse corresponding to the beginning of the magneticpattern the reproducing head |52 is moved with respect to the disk |00until the zero point on the scale |46 of the disk appears under the lamp|45. The switch |50 is then thrown to cut out the rectifier |5|. Theglow lamp now fires for the pulses corresponding to both the beginningand the end of the magnetic pattern, and two readings will be evident onthe face of the disk |00; one corresponding to the `start of theinterval to be timed will be evidenced by the zero point of the scale|46 being near the glow lamp |45, and the other corresponding to the endof the interval to be timed will be evidenced by a second view of thescale |46 apparently superposed on the first View of the scale M6. Thedifference between the two scale readings indicates the amount ofrotation of the disk |00 during the interval to be timed, and is also anindication of the duration of the interval. A network |55 may beprovided to equalize for losses in the rectiiier |5|..

In order to further avoid any chance of confusion in reading the anglethrough which the disk |00 rotates during the interval to be timed, asecond rectifier can be put in place of the corrective network |55. Thissecond rectifier should cut out the electromotive pulse of polarityopposite the polarity which the rectifier |5| cuts out, lthereby causingthe glow lamp |45 to flash only for electromotive pulses correspondingto the end of the magnetic signal. The switch |50 is thrown to connectthe reproducing head |52 to the glow lamp |45 through the rectier |5|thereby causing the'lamp to ignite in accordance with the start of themagnetic signal on the disk |00. The head |52 is rotated with respect tothe magnetizable disk |00 until the zero line of the scale |46 is inline with a mark such as |54 which is stationary. The switch |50 is thenthrown to- -connect the head |52 to the glow lamp |45 through the secondrectifier thereby causing the lamp to ignite in accordance with the endof the magnetic signal on the disk |00. With the glow lamp repeatedlyflashing under the control of the end of the magnetic signal, the valueof an angle will appear opposite the stationary mark |54. This angle isthe amount of rotation of the disk |00 during the interval to be timed,and is therefore an indication of the duration of the interval.

Instead of using a. iiashing Strobotron lamp and observing the timeduration on a rotating disk, a similar effect can be obtained by usingan electronic circuit such as is shown in Figure 10 wherein a. pulsecorresponding to the beginning of the magnetic pattern on the diskcauses a tube to become conducting. An integrating meter in the platecircuit of the tube will indicate the ow of current, and a second pulsecorresponding to the end of the magnetic pattern on the disk causes thetube to become nonconducting. The meter therefore will indicate f i dt:Since the plate current i can be made constant and the meter will thenmeasure time. The circuit for this device is shown in detail in Figure10 wherein the reproducing head |58 is associated with the magnetizabledisk |00 and establishes an electromotive force substantially inaccordance with the rate of change of magnetization in the disk |00. Theelectromotive force established in the reproducing head |50 is amplifiedby the ampliiier |60 and the output is connected to the Class Campliiler which is indicated generally by the reference character |6|.There are two portions |62 and |63 of the magnetic pattern on the disk|00 which exhibit a rapid rate of change, and the first |62 is at thestart of the signal and is in the opposite direction from the second |63which is at the end of the signal. That is, the rate of change |62 isdue to a rapid increase in the magnetic flux applied to the previouslydemagnetized disk |00 by the recording head, and the change |63 is dueto a rapid stopping of the magnetic flux applied by the recording head.Due to the fact that they are in opposite directions the twoelectromotive forces established during each revolution of themagnetizable disk may be made to appear as pulses of opposite polarity.The tube |64 functions as a phase inverter, and tubes |65 and |66 arebiased to beyond plate current cutoff. By using tubes |65 and |66 inpush-pull the first pulse established by the reproducing head |58 ispassed only by tube |65, and the second pulse is passed only by tube|66. The trigger circuit is indicated generally by the referencecharacter |61 and is comprised of two tubes |68 and |69 with theirassociated circuits, meter |10, and calibrating circuits. Normally thetrigger circuit is in such a condition that the tube |68 isnonconducting and tube |69 is conducting. This condition is maintainedbecause the voltage drop in the plate load resistor of tube |69 appliesa high negative bias to. tube |68. and the absence of plate current.through the plate resistors of tube |68 permits a positive bias to beapplied to tube |69. The ilrst pulse from the push-pull amplifier |6|applies a positive potential to the grid of tube |68 and current beginsto flow through the meter |10. This current produces a voltage drop inthe plate resistor of tube |68 and thereby biases tube |68 to cutoff.The second pulse applies a positive potential to the grid of tube |69,and the circuit is restored to normal with tube |68 nonconducting andtube |69 conducting. This entire process is repeated for each revolutionof the disk |00, and the meter |10 indicates the length of the magneticpattern on the disk by measuring the average current, through tube |68.The instrument is calibrated by adjusting the calibrating resistor |1|to cause the meter |10 to read full scale when tube |68 is conductingcontinuously. Pushing the calibrating button |12 biases tube |69 tocutofi thereby making tube |68 the conducting tube, and pushing therestoring button |13 biases tube |68 to cutoff.

Although I have described my invention with a certain degree ofparticularity, it is to be understood that the present disclosure hasbeen made only by way of example and that numerous changes in thedetails of construction and the combination and arrangement of parts maybe resorted to without departing from the spirit and the scope of theinvention as hereinafter claimed.

I claim as my invention:

1. A timing device comprising, in combination, record member means,means for driving the record member means at a known and constant rateof speed. meansfor providing an oscillating signal, means forcontrolling the duration of the signal in accordance with the intervalto be timed. rst and second recording means connected to said oscillatorand adaptedv to record on first and second portions of the recordmembermeans two patterns which together bear a direct relationship withthe length of the interval to be timed, counting means, first and secondreproducing means associated with said two portions oi the record membermeans, the first of said reproducing means establishing a. signal whichactuates said counting means and periodically blocks said first and saidsecond recording means, and means actuated by said second reproducingmeans for establishing a correction factor in accordance with the signalrecorded on said second portion by said periodically blocked secondrecording means which together with the indication on the counter meansprovides substantially an exact indication of the duration of the eventtimed.

2. A timing device comprising, in combination, magnetizable recordmember means, means for driving the record member means at a known andconstant rate of speed, means for providing an oscillating signal, meansfor controlling the duration of the signal in accordance with theinterval to be timed, first and second recording means connected to saidoscillator and adapted to record on first and second portions of therecord member means two magnetic patterns, iirst indicating means, rstand second reproducing means associated with said two portions of therecord memproducing means to said rst indicating means to' cause saidelectromotive force to actuate said first indicating means, secondindicating means, means connecting said second reproducing means to saidsecond indicating means for establishing a correction factor inaccordance with the signal* recorded on said second portion whichtogether with the indication on the first indication means providessubstantially an exact indication of the duration of the event timed.

3. A-timing device comprising, in combination, magnetizable recordmember means, means for driving the record member means at a known andconstant rate of speed, means for providing an oscillating signal, meansfor controlling the duration of the oscillating signal in accordancewith the interval to be timed, first and second recording meansconnected to said interval controlled source of oscillating signal andadapted to record on first and second portions of the record membermeans two magnetic patterns bearing a relationship to the interval to betimed, first and second reproducing means associated with said twoportions of the record member means forreproducing a signal therefrom,connection means from one of the said reproducing means to the saidrecording means to prevent said recording means from recording amagnetic pattern on said record member means while a previously recordedmagnetic pattern is passing said reproducing means, current supply meansconnected to the other of said reproducing means to establish saidreproducing means as an obliterating means durf ing the interval to betimed, first indicating means connected to the first of said reproducingmeans for giving a rough indication of the duration of the interval,second indicating means connected to said second reproducing means forestablishing a correction factor in accordance with the signal which wasrecorded on said second portion of the magnetic member means and whichwas not obliterated during the interval to bc timed, said first andsecond indicating means together providing substantially an exactindication of the duration of the event timed.

4. The process of measuring a time interval comprising the steps ofproviding record member means moving at a known and constant rate ofspeed, providing a signal, controlling the signal in accordance with theinterval to be timed, recording on two portions of the record membermeans two patterns which bear a relationship to the interval controlledsignal, counting whole numbers in accordance with one of said patterns,repeatedly reproducing only the other pattern to determine a. fractionalnumber, and utilizing said whole number and said fractional number toprovide an indication of the duration of the time interval.

5. The process of measuring a time interval comprising the steps of:providing record member means moving at e. known and constant rate ofspeed, providing a signal, controlling the signal in accordance with theinterval to be timed, recording on two portions of the record membermeans two patterns, said two patterns together bearing a directrelationship to the length of the interval to be timed, utilizing one ofsaid natterns to provide a rough indication of the duration of theinterval. and utilizing the two patterns together to providesubstantially an exact indication of the duration of the interval to betimed.

6. The process of measuring a time interval comprising the steps of:providing record member means moving at a known and constant rate ofspeed, providing a signal, controlling the signal in accordance with theinterval tobe timed. recording on two portions of the record membermeans two patterns, said two Patterns together bearing a directrelationship to the length of the interval to be timed, actuating acounting device in accordance with one of said patterns to provide arough indication of the duration of the interval, and repeatedlyreproducing a portion of only the other of said patterns to establish acorrective value which together with the rough indication providessubstantially an exact indication of the duration of the time interval.

7. A timing device comprising, in combination, record member means,means for driving the record member means at a known and constant rateof speed, means for providing a signal, means for controlling the signalin accordance with the interval to be timed, first and second recordingmeans adapted to record on first and second portions of the recordmember means two patterns which together bear a direct relationship tothe length of the interval to be timed, counting means actuated by therst of said patterns to provide a rough indication of the duration ofthe time interval, and means for repeatedly reproducing a portion ofonly the second pattern to establish a correction value which togetherwith the rough indication provides substantially an exact indication ofthe duration of the time interval.

8. A timing device comprising, in combination, record member means,means for driving the record member means at a known and constant rateof speed, means for providing a signal, means for controlling the signalin accordance with the interval to be timed, first and second recordingmeans adapted to record on first and second prtions of the record membermeans two patterns which together bear a direct relationship to thelength of the interval to be timed, counting means actuated by the firstof said patterns to provide a rough indication of the duration of thetime interval, indicating means actuated by a portion of only the secondof said patterns to establish a correction value which together with therough indication provides substantially an exa-ct indication of theduration of the time interval, and control means connected to saidcounting means and to said second recording means for influencing thesaid second pattern in accordance with the said first pattern.

9. In a timing device, a record member, means for cyclically driving therecord member at a known and constant rate of speed, recording meansassociated with said record member, a source of alternating signalconnected to said recording means, means for controlling the duration ofthe signal applied to said recording means in accordance with theduration of the interval to be timed, reproducing means associated withsaid record member for reproducing the signal recorded thereon onceduring each of a succession of cycles of motion of said record memberpast said reproducing means, calibrated signal averaging means, andelectronic means connected to said reproducing means and to said signalaveraging means, said electronic means including the following elements,an amplifier for amplifying the signal obtained from said reproducingmeans and a limiter for limiting the peaks of said amplified signal, atleast one of said elements being biased to cause the element to passonly signals above a certain amplitude.-

10. In a timing device, a record member, means for cyclically-drivingthe record mem y known and constant rate 'of speed. ".r'e'cording meansassociated with said recordmember, a sourcefof alternating signalconnected to said recording means, means for controlling the duration ofthe signal applied to said recording means in accordance with theduration of the interval to be timed, reproducing means associated withsaid record member for reproducing the signal re' corded thereon onceduring each of a succession of cycles of motion of said record memberpast said reproducing means, calibrated signal averaging means, andelectronic means connected to said reproducing means and to said signalaveraging means, said electronic means including the following elements,an amplifier for amplifying the signal obtained from said reproducingmeans, a limiter for limiting the peaks of said amplified signal, and arectifier, at least one of said elements being biased to cause theelement to pass only signals above a certain amplitude.

11. The invention as set forth in claim 10, further characterized inthis: that it is the said rectifler which is biased to pass only signalsabove a certain amplitude.

12. The invention as set forth in claim 9, further characterized inthis: that the said certain amplitude above which the element passessignals is chosen in accordance with the magnitude of the backgroundnoise of the system such that substantially no signal corresponding tothe said background noise is passed to the signal averaging means.

13. A timing device comprising, in combination, a magnetizable recordmember, means for cyclically driving the record member at a known andconstant rate of speed, magnetic recording means associated with saidrecord member, a source of alternating signal connected to saidrecording means, means for controlling the duration of the signalapplied to said recording means in accordance with the duration of theinterval to be timed, magnetic reproducing means associated with saidrecord member for reproducing the signal recorded thereon once duringeach of a succession of cycles of motion of said record member past saidreproducing means, calibrated signal averaging means, and electronicmeans connected to said reproducing means and to said signal averagingmeans, said electronic means including the following elements, anamplifier for amplifying the signal obtained from said reproducing meansand a limiter for limiting the peaks of said amplified signal, at leastone of said elements being biased to cause the element to pass tion, amagnetizable record member, means forcyclically driving the recordmember at a known and constant rate of speed, magnetic recording meansassociated with said record member, a source of alternating signalconnected to said recording means, means for controlling the duration ofthe signal applied to said recording means in accordance with theduration of the interval to be timed, magnetic reproducing meansvassociated with said record member for reproducing the signal recordedthereon once during each of a succession of cycles of motion of saidrecord member past said reproducing means, calibrated signal averagingmeans, and electronic means connected to said reproducing means and tosaid signal averaging means, said electronic means including thefollowing elements, an amplifier for amplifying the signal obtained fromsaid reproducing means, a limiter for limiting the peaks Vof saidamplified signal, and a rectifier, at least one of said elements beingbiased to cause the element to pass only signals above a certainamplitude.

l5. 'I'he invention as set forth in claim 14, further characterized inthis: that it is the said rectifier which is biased to pass only signalsabove a certain amplitude.

16. The invention as set forth in claim 13, further characterized inthis: that the said certain amplitude above which the element passessignals is chosen in accordance with the magnitude of the backgroundnoise of the system such that substantially no signal corresponding tothe said background noise is passed to the signal averaging means.

17. The process of measuring the duration of a time interval comprisingthe steps oi' providing a record member, cyclically driving the recordmember at a known and constant rate of speed, providing a source ofalternating signal, controlling the duration of the alternating signalin accordance with the duration of the interval to be timed, recordingon said record member a signal bearing a relationship to the duration ofthe interval controlled signal, repeatedly reproducing the recordedsignal during successive cyclic motions of said record member,amplifying the reproduced signal, limiting the peaks of the amplifledsignal, providing calibrated signal averaging means, and passing to saidcalibrated signal averaging means only that portion of the ampliiled andlimited reproduced signal which exceeds a certain value wherebyerroneous actuation of said signal averaging means due to backgroundnoise is reduced.

18. The yprocess as set forth in claim 17, further characterized inthis: that the said reproduced signal is also rectified before it isapplied to the said signal averaging means.

19. The process as set forth in claim 17, further characterized in this:that the said reproduced signal is also rectified before it is appliedto the said signal averaging means, and the rectifier means is biased topass to the calibrated signal average means only that portion of theamplified and limited reproduced signal which eX- ceeds the said certainvalue.

20. The process as set forth in claim 17, further characterized in this:that the said record member is a magnetizab'le member and the recordingand reproducing steps are steps of magnetically recording andreproducing.

2l. The process of measuring a time interval comprising the steps of:lproviding a record mem ber, providing means for recording a signal onsaid record member, establishing a known and constant rate of relativemotion between said record member and said recording means, providing asignal, controlling the signal in accordance with the duration of theinterval to be timed, recording the controlled signal on said recordmember while there is relative motion between said record member andsaid recording means, repeatedly reproducing the record from the recordmember to establish a reproduced signal, amplifying the reproducedsignal, detecting the reproduced signal, limiting the amplitude of theamplified reproduced signal, providing calibrated signal averagingmeans, and passing to said signal averaging means only that portion ofthe amplined, limited, and detected reproduced signal which exceeds acertain value whereby erroneous actuation of said signal averaging meansdue to background noise is reduced.

22. The invention as set forth in claim 21, further characterized inthat the record member is magnetizable and said recording andreproducing steps are steps of magnetically recording and reproducing.

23. The invention as set forth in claim 21, further characterized inthat the duration of the signal which is provided is controlled inaccordance with the duration of the interval to be timed.

24. The process of measuring a time interval comprising the steps of:providing record member means, cyclically driving the record membermeans at a known and constant rate of speed. providing an electricalsignal, controlling the duration of the electrical signal in accordancewith the duration of the interval to be timed, recording on two portionsof the record member means at least two signals derived in accordancewith the interval controlled electrical signal, indicating timeintervals of a known duration in accordance with at least one of saidrecorded signals, and repeatedly utilizing at least the other of saidrecorded signals to measure a time interval shorter than the interval ofknown duration, the duration of said interval to be measured beingdetermined with a high degree of accuracy by utilizing together theindication of said intervals of known duration and said indication ofthe shorter time interval.

25. The process as set forth in claim 24 wherein the indication of thesaid shorter interval is algebraically added to the sum of the said timeintervals of known duration.

26. The process as set forth in claim 4, further characterized in thatthe signal is magnetically recorded and reproduced.

27. The process as set forth in claim 5, further characterized in thatthe signal is magnetically recorded and reproduced.

SENII JOSEPH BEGUN.

